What is low/medium/high flow?

[less than bread]

Key aspects to reef keeping are flow and light and corals are often described as preferring either low, medium, or high levels of each. Unlike light, however, it's very difficult to actually measure how much flow a coral is getting. I'm sure everyone has their preferred ways of setting up the flow in their tanks and determining flow I feel like is an art more than a science.

 

For me, I think of three descriptive words for each level of flow:

 

Whipping = High

Dancing = Medium

Waving = Low

 

Let's talk about flow. How do you determine the kind of flow your corals are getting? How do you have your return nozzle and powerheads configured? For you, what does low/medium/high mean? How do you determine if a coral is getting too much/too little flow?

[ReefTaco]

If I remember correctly it's The volume of the tank turned over in gph

 

Low = 10-20x

Moderate =20-30x

High =30+

 

So for like 10gallon tank

A powerhead of 100-200gph is low

200-300is moderate

And 300+ gph is high

 

I'm sure there are more factors like wave pulsing and direction but I guess that's like a basic rule or base line when selecting a pump

[PeterU]

18 minutes ago, Instant_taco said:

If I remember correctly it's The volume of the tank turned over in gph

 

Low = 10-20x

Moderate =20-30x

High =30+

 

So for like 10gallon tank

A powerhead of 100-200gph is low

200-300is moderate

And 300+ gph is high

 

I'm sure there are more factors like wave pulsing and direction but I guess that's like a basic rule or base line when selecting a pump

Best I've ever heard.

[Clown79]

14 hours ago, Instant_taco said:

If I remember correctly it's The volume of the tank turned over in gph

 

Low = 10-20x

Moderate =20-30x

High =30+

 

So for like 10gallon tank

A powerhead of 100-200gph is low

200-300is moderate

And 300+ gph is high

 

I'm sure there are more factors like wave pulsing and direction but I guess that's like a basic rule or base line when selecting a pump

This 100%

[ReefTaco]

The tricky part is to keep everyone happy with not to many dead spots

[Murphs_Reef]

Let me use that calc for a second: 

Low = 10-20x

Moderate =20-30x

High =30+

 

We tend now to use the return value (that's turnover). 

 

Im at 92gal total volume, 

• Nero running @ 1220 gph.
• Jecod @ about 1750 gph

That brings me out at 2970 = 32 times. 

 

Add the Return @ 2000 gph though

 
4970 = 54 times.. no wonder my torch is 5 miles long 🤣

[InAtTheDeepEnd]

🤨 

An alternative view 

 

Not saying it's right btw - just putting it out there! 

 

 

[ReefTaco]

39 minutes ago, InAtTheDeepEnd said:

🤨

An alternative view 

 

Not saying it's right btw - just putting it out there! 

 

 

That is a lot of flow lol but it's not too far off I had a 425gph circulation pump in my 5 gallon which is 85x plus my return so I'd say 116x but it was a little too much flow for my taste so I dropped it down to a 290gph pump. Also my return is 159gph so I'm at 85x more or less but direction is key my circulation pump is pointing up and water is colliding with the return flow so it makes a swirl type wave but it's random ish. Everyone is happy in my tank. What cool is I would say my tank had all three types of flow  

 

Red is area is high flow

Blue is the moderate area

And purple is the low flow area

 

Flow can be tricky sometimes

[Murphs_Reef]

1 hour ago, InAtTheDeepEnd said:

🤨

An alternative view 

 

Not saying it's right btw - just putting it out there! 

 

 

That'll be SPS that.. put that on LPS you'll have some lovely skeletons, mushrooms would be stuck to the glass and zoas wouldnt open. 

 

Oh hold on.. that's turnover. Is that being used interchangeably here?

Turnover - water passing through the sump / filter area..

Flow rate - powerheads, wavemakers, internal movement. 

[ReefTaco]

16 minutes ago, Murphych said:

That'll be SPS that.. put that on LPS you'll have some lovely skeletons, mushrooms would be stuck to the glass and zoas wouldnt open. 

 

Oh hold on.. that's turnover. Is that being used interchangeably here?

Turnover - water passing through the sump / filter area..

Flow rate - powerheads, wavemakers, internal movement. 

We're talking about flow, I say turnover as an measure for the low, moderate, high, when compared to the tanks size. But your probably right sorry for the confusion. But return pump flow is part of a tanks overall flow equation

[Murphs_Reef]

26 minutes ago, Instant_taco said:

We're talking about flow, I say turnover as an measure for the low, moderate, high, when compared to the tanks size. But your probably right sorry for the confusion. But return pump flow is part of a tanks overall flow equation

Yeah far cop. I don't include return as my internal flow, that's always just been the way I learned to think about it. So almost forget it's there.. but there are schools of thought,

There's a good write up on R2R:

 

Oh that and to buy pumps that significantly exceed your requirements, so they don't need to be turned up to max. 

 

Either way in my example, I'm in the high area. 

[ReefTaco]

1 hour ago, Murphych said:

Yeah far cop. I don't include return as my internal flow, that's always just been the way I learned to think about it. So almost forget it's there.. but there are schools of thought,

There's a good write up on R2R:

 

Oh that and to buy pumps that significantly exceed your requirements, so they don't need to be turned up to max. 

 

Either way in my example, I'm in the high area. 

True But in my case my tank is so small I noticed a big change in flow when I upgraded my return pump so I kind of have to include the flow from my return cause it actually has a big impact. I can see that not being a case for bigger tanks.   

 

Also thanks for the article

 

 

 

Also I just thought of this meme hehe

 

 

[less than bread]

Good stuff everyone. Thanks for contributing. I was having a heck of a time getting the flow right in my new tank. With the return at the lowest setting, it was still blasting everything even with the powerhead turned off, especially things low in the tank. The flow would hit the front glass and then shoot down to the bottom. I just had a RFG nozzle right after the outflow so the flow coming out was super strong and moving in one direction. After a few days and many corals looking mad, I thankfully remembered and found the old dual duckbill nozzle from my Evo. Using that instead of just the single RFG has helped so much because it splits and disperses the flow much better.

[mcarroll]

On 10/21/2021 at 4:55 PM, less than bread said:

For you, what does low/medium/high mean? How do you determine if a coral is getting too much/too little flow?

On 10/21/2021 at 8:53 PM, Instant_taco said:

If I remember correctly it's The volume of the tank turned over in gph

On 10/25/2021 at 9:22 AM, InAtTheDeepEnd said:

What turnover of tank volume is rule of thumb for a reef tank?

 

Well, it's a good question.  I wish the answer was as simple as "32X" or something like that.

 

Consider that in the early days, a stock 300gph MaxiJet would have been too much flow for a small reef tank.  You could use a few of them strategically in a larger tank.  But in a small tank, the high-velocity flow (designed to ram water through plumbing) was murder to anything that was in it's line of sight.

 

So what was that "turnover" like from a pump that was "too much"?

 

300gph / 20 gallons = 15x turnover.  30x in a 10 gallon would have been completely ridiculous.

 

(Worth noting, this ultimately prompted the development of MaxiJet conversion kits to turn that high-velocity 300gph into much lower-velocity propellor-based pump that was moving closer to 1200gph.)

 

Fast forward in time and the pump makers have lowered the output pressure so much on some pumps (inflating the GPH number in the process) that there's almost no way to compute a sensible GPH number or "turnover" number without also specifying the exact pump you're going to be using.  (Which makes handy things like universally usable "turnover" numbers pretty much impossible.)

 

The Tunze folks had the first commercial propellor pumps.  Their 6045 and 600x pumps are still among the best flow pumps ever made for reefing.  Keeping our conversation to smaller tanks, their 6045 puts out around 1100gph.

 

Ecotech came later with their "3200gph" Vortech pump, which cost about 3x as much as the 6045 I mentioned.  (The Vortech was positioned, price-wise, against Tunze's larger 600x series.)

 

What never really got published with much "oomph" was that while the gph numbers were going up, the amount of work the pumps were doing in the tank was going down.

 

Yes a "3200gph" Vortech might move the same "3200gph" that a Tunze 6105 would move.

 

But GPH doesn't measure the ability to do work....velocity does.  (...which is measured in something like centimeters per second or feet per second.)

 

The Vortech will only do its "3200gph" about 24" in front of the pump, and nowhere else in the tank.  

 

By comparison, the 6105 can spread that same "gph" over a five or six foot tank.

 

I was running a 38 Gallon and (later) a 50 Gallon tank with two Tunze 6045's (total of 2200gph) when the Vortechs came out, and the tank needed an upgrade because corals had grow so dense that flow was suffering in several areas of the tank.

 

I coincidentally had access to a second-hand pair of Gen2 Vortechs, which on paper, both combined, should have generated somewhere North of 6000gph.  So I tried them in place of the 6045's.

 

Flow in the tank was even worse than it was with the 6045's.  Why?

 

Because the ultra-soft flow of the Vortechs was incapable of penetrating the coral canopy in my tank – even less capable that pumps with only 1/3 of the Vortech's "gph" rating.  I was baffled and tried everything I could to make these pumps act like "6000gph", moving them, etc.  The two 6045's were always slightly better than the two Vortechs, even at their best.

 

The 6045's have a nice, medium output force that will carry it's "1100gph" flow three or four feet.

 

I ended up adding a third 6045, bringing my total "gph" in the tank up to "3300gph" on paper...still less than a single Vortech's "gph" rating, but flow become phomenal in the tank (once again) with the third 6045.

 

That's ancient history because, of course, now there are dozens of flow pumps available with widely varying characteristics...not just those two.

 

Velocity still does the work for each brand though....not "gph".

 

Check this out:

 

[ReefTaco]

2 hours ago, mcarroll said:

 

Well, it's a good question.  I wish the answer was as simple as "32X" or something like that.

 

Consider that in the early days, a stock 300gph MaxiJet would have been too much flow for a small reef tank.  You could use a few of them strategically in a larger tank.  But in a small tank, the high-velocity flow (designed to ram water through plumbing) was murder to anything that was in it's line of sight.

 

So what was that "turnover" like from a pump that was "too much"?

 

300gph / 20 gallons = 15x turnover.  30x in a 10 gallon would have been completely ridiculous.

 

(Worth noting, this ultimately prompted the development of MaxiJet conversion kits to turn that high-velocity 300gph into much lower-velocity propellor-based pump that was moving closer to 1200gph.)

 

Fast forward in time and the pump makers have lowered the output pressure so much on some pumps (inflating the GPH number in the process) that there's almost no way to compute a sensible GPH number or "turnover" number without also specifying the exact pump you're going to be using.  (Which makes handy things like universally usable "turnover" numbers pretty much impossible.)

 

The Tunze folks had the first commercial propellor pumps.  Their 6045 and 600x pumps are still among the best flow pumps ever made for reefing.  Keeping our conversation to smaller tanks, their 6045 puts out around 1100gph.

 

Ecotech came later with their "3200gph" Vortech pump, which cost about 3x as much as the 6045 I mentioned.  (The Vortech was positioned, price-wise, against Tunze's larger 600x series.)

 

What never really got published with much "oomph" was that while the gph numbers were going up, the amount of work the pumps were doing in the tank was going down.

 

Yes a "3200gph" Vortech might move the same "3200gph" that a Tunze 6105 would move.

 

But GPH doesn't measure the ability to do work....velocity does.  (...which is measured in something like centimeters per second or feet per second.)

 

The Vortech will only do its "3200gph" about 24" in front of the pump, and nowhere else in the tank.  

 

By comparison, the 6105 can spread that same "gph" over a five or six foot tank.

 

I was running a 38 Gallon and (later) a 50 Gallon tank with two Tunze 6045's (total of 2200gph) when the Vortechs came out, and the tank needed an upgrade because corals had grow so dense that flow was suffering in several areas of the tank.

 

I coincidentally had access to a second-hand pair of Gen2 Vortechs, which on paper, both combined, should have generated somewhere North of 6000gph.  So I tried them in place of the 6045's.

 

Flow in the tank was even worse than it was with the 6045's.  Why?

 

Because the ultra-soft flow of the Vortechs was incapable of penetrating the coral canopy in my tank – even less capable that pumps with only 1/3 of the Vortech's "gph" rating.  I was baffled and tried everything I could to make these pumps act like "6000gph", moving them, etc.  The two 6045's were always slightly better than the two Vortechs, even at their best.

 

The 6045's have a nice, medium output force that will carry it's "1100gph" flow three or four feet.

 

I ended up adding a third 6045, bringing my total "gph" in the tank up to "3300gph" on paper...still less than a single Vortech's "gph" rating, but flow become phomenal in the tank (once again) with the third 6045.

 

That's ancient history because, of course, now there are dozens of flow pumps available with widely varying characteristics...not just those two.

 

Velocity still does the work for each brand though....not "gph".

 

Check this out:

 

This guy flows ☝️

[mcarroll]

If anyone wants to nerd out (some more) on this topic I've got some very nerdly articles on flow (or things closely related to it) saved here.

 

Here's one of my favorites (and one that dovetails perfectly with the Tunze video I linked earlier) but there really are a BUNCH of good articles marked for that section:

"Function of Funnel-Shaped Coral Growth in a High-Sedimentation Environment"

 

(After all the words in that post, I never mentioned why flow is important....and that is something that is often taken for granted or even overlooked completely.  This article will dial in why flow is important to corals.  The "Oceanic Forcing..." article (not linked here) is good on this too....gives more of a "30,000 foot view".  Even if you're already familiar with the term "boundary layer" there's probably some interesting reading in these articles!!)